This longitudinal study investigates the morphosyntactic development of the noun phrase in two young Bosnian/English bilingual children (both girls, aged 1.8 to 2.4). as well as their pragmatic development, in light of the 'single system' and the 'separate system' hypotheses. Although both of the children are acquiring the two languages simultaneously, the contexts of acquisition are different. Rina's parents speak different native languages - the mother speaks English and the father Bosnian - and claim that they employ the 'one person, one language' strategy when interacting with their daughter. The second child, Anya, is exposed to Bosnian at home, as both of her parents are native Bosnian speakers, and English only at the nursery. The relationship between the children's degree of mixing in the two languages and the discourse strategies employed by the parents/caretakers is also examined. The parental strategies are categorised as either being monolingual or bilingual (Lanza, 1992,1997a). Both the Minimal Grasp and the Expressed Guess Strategies are requests for clarification and are classified as monolingual strategies. The Minimal Grasp Strategy enables the parent or carer to negotiate a monolingual context with his or her child, thus feigning the role of a monolingual. With the Expressed Guess Strategy, it is the parent who attempts to reformulate the child's mixed utterance; he/she does not request that from the child, as is the case when a Minimal Grasp Strategy is employed. The last three strategies identified by Lanza ( 1992; 1997a) - Repetition Strategy, Move on Strategy and Code- Switching Strategy - are defined as being bilingual strategies, as they reveal the parent's bilingual identity by clearly indicating the parent's comprehension of the child's mixed utterance. The results show that both bilingual children are able to differentiate their two languages according to context (pragmatic differentiation), as well as structurally, from the earliest stages. There is appropriate inflectional marking within the noun phrase in Bosnian from the beginning, whereas marking is appropriately absent in English. The fact that the children are not recorded using either Bosnian inflections within an English noun phrase in the English context, or English inflections within a Bosnian noun phrase in the Bosnian context, thus serves as evidence for the 'separate system' hýpothesls. Further evidence is provided by the low percentage of mixed utterances in the data for both children. The presence of a slightly higher number of English, as well as mixed, utterances in Anya's data in the Bosnian context can be explained by the fact that the parents are found to be negotiating a bilingual context of interaction in the home, by using certain discourse strategies which signal to Anya that the use of English items in the Bosnian context is acceptable. On the other hand, a much lower number of mixed utterances is recorded in Rina's data. Rina's parents generally adhere to the 'one person, one language' strategy, although the mother employs more bilingual than monolingual strategies in response to the child's context-inappropriate language use than the father, resulting in a higher percentage of Bosnian utterances being recorded in the English context. These findings suggest that the parents' pragmatic choices may also have an influence on the language development of bilingual children.